Hitherto, architects in their drawings of corridor walls adjacent elevator shafts of buildings have assigned dimensions to the rough opening into which the finished entrance opening structure or framework is subsequently installed. Frequently the corridor wall opening constructed by following these dimensions has left inadequate clearances between the edges of the opening and the finished entrance opening framework for the elevator-installing workmen to insert their wrenches and other tools. This prior procedure also has consumed an excessive amount of time in custom-building the elevator shaft and entrance openings thereto and requires constant vigilance on the part of the masons and foremen to insure that these rough openings are neither too large nor too small. Furthermore, the installation of the entrance framework into the rough opening has incurred damage to this finished framework by workmen passing through the entrance opening, such as by their wheelbarrows scraping the finished metal work.